doubled cable on a radial

[Ducksy]

Hey guys I see this now and again on my rounds....8.5kw method C on 2 x 2.5mm cable......does it state anywhere in the regs that it a radial must be a single cable Or is it acceptable ? the very least i think its lazy not using 6mm but as always I'm well off from the more experienced guys think

Thanks

 

[RyanCheetham]

You can run cables in parralell but they must be identical with the same resistance values

 

[Ducksy]

Sweet would you say that the cables CSA totals 5mm.....as it could be the case the CCC is not sufficient.

 

[telectrix]

and the cables must take the same route. if protected with a 40A MCB, the cables should not be overloaded, method C, but , not good practice, IMO.

 

[RyanCheetham]

Yes the csa would be 5mm

 

[Ducksy]

Great that's what I was thinking thanks tele and Ryan

 

[Guitarist]

I've seen that method of supply to old garage fuseboards on a 30A fuse, but never to a shower.

 

[sparkymalarky]

What happens when the shower is replaced with a 500kW unit? Kablammo. height of laziness! who be arsed pulling in and clipping 2x2.5mm² cables when 1 x 6mm² would have been handier, easier, safer etc.

 

[Fin170]

What happens when the shower is replaced with a 500kW unit? Kablammo. height of laziness! who be arsed pulling in and clipping 2x2.5mm² cables when 1 x 6mm² would have been handier, easier, safer etc.

Going to need, probably, at least 2x6mm I think......or it's own power station :lol:

 

[sparkymalarky]

A good 10mm² will sort it out. :21:

But getting back to the point, not ideal, but if they are on a 40A protective device, no rules being broken technically.

 

[Ducksy]

I've seen it quite a few times......realistically this is a ring final circuit.....just with one point.

 

[kingeri]

Poor practice but not against the regs as far as I know. As said though, why do it?

 

[Guitarist]

Poor practice but not against the regs as far as I know. As said though, why do it?

They probably had a reel of 2.5mm from the RFC and didn't want to pay for a length of 6 or 10mm

 

[markythesparky]

How would you work out the current carrying capacity of this set up? If its a ring then the maximum overcurrent device allowed is 32a, but this is 5mm??!?!?! where is this cable in BS7671.

Also what happens when one of the phase or neutrals comes out?

i wouldnt be thinking this is an acceptable way of doing things but hey this is why this forum is here!

 

[Ducksy]

How would you work out the current carrying capacity of this set up? If its a ring then the maximum overcurrent device allowed is 32a, but this is 5mm??!?!?! where is this cable in BS7671.

Well i figured method c 4mm = 37a

6mm = 47a

so i'd say 42a for 5mm

 

[markythesparky]

Sounds like a guess. If its not in BS7671 and you can tget information from the manufacturer then you will be guessing.

Although 2.5mm is rated around 27A (clipped direct and depending on its run), the ring will not necessarily put equal load on each cable and hence the 32A device. In your case the cables may well be the same length and therefore in theory should split the load equally. But this does not take into account resistance at the terminations. again this is an unknown. in the event that one side comes free, a 32A MCB will be just enough to protect the cable. In your sitaution it will not be and you will have a fire.

You cant back yourself up in a court case with guesswork. If you go by BS7671 then you will not have unknowns and you will not be guessing. No one will be able to argue.

 

[amlu]

how about just treating that radial as a ring, with single accessory connected at the end of it?
if its sits on its own 32a breaker should be up to the regs?

 

[markythesparky]

Would be better and obviously safer.

BUT.... 8.5Kw / 230v is 36.96amps.

Still think this is an option?

 

[decolad69]

What next? I'll wire my shower in 4x 1.5mm all the same length and taking the same route arty:

 

[Guest55]

unorthodox but no problem at all using 2 feeds to a fixed equipment so long as they're the same length ( for load balancing reasons ) and both cables are wired into the same terminals at the CU ( for identification purposes )